A Standard Unicycle

Unicycles aren't too popular on the roads for the simple reason that they are not very efficient form of transportation, beside looking like a clown riding one. Good for party tricks and entertainment but that's all.

Picture source: http://foolawecon.files.wordpress.com

A Clown's Bicycle - With Old Boots Rear Wheel

Clowns and bicycles seem to be made for each other! I know many cyclists who are clowns, but this one that I found takes the biscuit. The rear wheel is made up of old boots, I bet it works as well. I'm sure it moves slowly hence no brakes

Source: http://www.metzbicyclemuseum.com